Use of a polymer additive to improve the optical brightener absorption characteristics of durable-press fabrics

ABSTRACT

A COTTON FABRIC IS TREATED WITH A SOLUTION CONTAINING POLYVINYLPYRROLIDONE-POLYACRYLATE COPOLYMER AND A CROSSLINKING AGENT WITH SUITABLE CATALYST TO PRODUCE A DURABLE PRESS FABRIC WHICH POSSESSES THE IMPARTED DESIRABLE QUALITY OF BEING ABLE TO ABSORB OPTICAL BRIGHTENERS NORMALLY INCLUDED IN LAUNDRY DETERGENTS. A WHITE FABRIC TREATED BY THE PROCESS OF THIS INVENTION IMPROVES IN WHITENESS WITH REPEATED LAUNDERINGS. WHEN THE FORMULATION IS SUPPLEMENTED WITH LOW AMOUNTS OF POLYPROPYLENE GLYCOL AND ALKYL ETHYLENEOXIDE ALCOHOL THE PERFORMANCE OF THE TREATED GARMENT OR FABRIC IS FURTHER ENHANCED.

United States Patent 3,702,230 USE OF A POLYMER ADDITIVE TO IMPROVE THE OPTICAL BRIGHTENER ABSORPTIUN CHARAC- TERISTICS 0F DURABLlE-PRESS FABRICS Eugene J. Blanchard, New Orleans, and Gloria A. Gautreaux and Robert .I. Harper, Jr., Metairie, 1.2., assignors to the United States of America as repre sented by the Secretary of Agriculture No Drawing. Filed Jan. 7, 1971, Ser. No. 104,782 Int. Cl. D06rn 15/36, 15/58 US. Cl. 8-100 6 Claims Wm... .ru

ABSTRACT OF DISCLOSURE A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to the treatment of cellulosic textiles with improved crosslinking formulations. More particularly, this invention relates to the treatment of cotton and other cellulosic fabrics with solutions containing certain proportions of polyvinylpyrrolidone-polyacrylate copolyrner in combination with a crosslinking agent and a suitable catalyst to produce a finished fabric or garment which in addition to having the qualities of durable press also is able to absorb optical brighteners from normal laundry detergents. The formulations are further improved upon addition of small quantities of polypropylene glycol and alkyl ethyleneoxide alcohol in that the treatment of fabrics with the improved formulations yields further improved all-around performance.

The main object of this invention is to provide a chemical treatment for imparting to cellulosic fabrics simultaneously the desirable properties of wrinkle resistance and ability to absorb optical brighteners from laundry detergents during laundering of the treated fabrics or garments.

A second object of this invention is to provide through the addition of supplementary ingredients in the same bath further improvements in the finished products of the main object.

In developing the treatments of this invention it was noted that with the ability to absorb optical brighteners the treated fabrics would tend to increase in whiteness upon repeated launderings. In this manner a more washable cellulosic textile product was produced. This property of absorbing optical brighteners from detergents can be imparted to fabrics by incorporating in the pad bath solution certain amounts of polyvinylpyrrolidone-polyacrylate copolyrner. In addition to improving the adsorption of optical brightener the polymer makes a contribution to wrinkle recovery performance thus permitting the use of lower than normal amount of crosslinking agent in the pad bath formulation.

Heretofore, it is well known that normally crosslinked durable press or wash-wear fabrics have a small capacity to renew their whiteness by absorbing the optical brighteners from everyday laundry detergents. While it is common practice to try to overcome this deficiency by adding the optical brightener to the crosslinking solution, this approach has certain deficiences. First, the alkaline chemical nature of many optical brighteners limits their application due to the fact that they tend to neutralize the acid catalyst. This may lead to a poorer durable press appearance. The second limitation is that the high temperatures used in curing may lead to discoloration of the brightener. Finally, with time, discoloration or graying in the fabric may occur due to slow removal of the original optical brightener.

Certain reactive alcohol additives improve optical brightener absorption but reaction efficiency tends to limit the cost effectiveness of this approach. The use of a polymer additive such as the polyvinylpyrrolidone-acrylate copolyrner permits the use of relatively low amounts in finishing formulation due to improved efficiency. Moreover, because the polymer makes a contribution to wrinkle recovery, a reduced level of crosslinking agent can be used in the formulation.

We have now found that by incorporating certain amounts of the polymer in the pad bath it is possible to produce durable press or wash-wear fabrics which will absorb the optical brighteners in laundering using common detergents. A distinct copolymer type seems to be required to accomplish this property. One monomer is vinylpyrrolidone, the other is an acrylate or methacrylate monomer. These latter should be such that the pendant R-groups are from 4-18 units in length. The choice of the R-groups should be such that the resulting copolyrner should have a low glass transition temperature. This low glass transition temperature is necessary so that the copolyrner can make an improvement to fabric wrinkle recovery performance. The copolyrner nature of the polymer is required for good optical brightener absorption because a structure combination that is partly hydrophilic and partly hydrophobic has been found to be preferred for this type of performance. Thus, polyvinylpyrrolidone itself it water-soluble and would not be retained on the fabric. Polyacrylates by themselves have not been found to improve optical brightener absorption.

The preferred polymer structure then is A, in which either acrylate or pyrrolidone may follow itself or the other moiety in the final polymer chain.

x and y can be varied. Each can be from 30-70% of total monomer units, that is x=30 to 70% of monomer units y=l00% -x or 70% to 30% of monomer units While the copolyrner is effective over varying monomer ratios, the preferred structure would appear to be one in which each component represents between 30-70% of the total monomer units in the chain. The ratio should be adjusted (depending upon R group) so that the resulting polymer will have a low glass transition temperature.

The copolymer is relatively durable on the fabric to laundering. As a consequence of this phenomenon, the fabric after 10 launderings, was noticeably whiter than a similar fabric treated with a crosslinking formulation without the copolymer additive. Another means by which the effect of the copolymer can be demonstrated is by inspection of the fabrics under ultraviolet light. Under these conditions, a cured fabric prepared from sensitized fabric treated in a conventional manner was gray. On the other hand, the sample prepared from sensitized fabric treated with a solution containing the polyvinylpyrrolidone-acrylate copolymer was white under ultraviolet light. This demonstrates the ready absorption of optical brighteners to the latter fabric. These results were readily observed on fabric washed as many as times, thus illustrating the durable nature of this treatment.

Another method by which the increased absorption of optical brighteners can be determined is to measure the fluorescence of the fabric using a suitable apparatus such as a Farrand Spectrofluorometer. By this method the crosslinked control with no polymer additive had 11% of the fluorescence of the untreated cotton control with no crosslinking treatment. By contrast the samples treated with 0.5% to 4% of polyvinylpyrrolidone-acrylate copolymer had fluorescent values ranging from 22 to 49% of the untreated cotton. If 1% of polypropylene glycol (mol. wt.=340) and 1% of alkyl ethyleneoxide alcohol (-alkyl group is C-12, 60% of additive molecular weight due to ethylene oxide component) were included in these formulations with the copolymer and crosslinking agent, then fluorescence and hence optical brightener absorption was from 41-62% of the untreated cotton control. A somewhat parallel set of values was observed for samples measured on the spectrofluororneter after 10 washings.

Besides the increased aflinity for optical brighteners, the polyvinylpyrrolidone-acrylate copolymer improves the wrinkle recovery and tearing strength of crosslinked fabric.

In addition to the process outlined above, a variation from contemporary textile practice can be performed. In this case, both the polyvinylpyrrolidone-acrylate copolymer and an optical brightener are included with the crosslinking agent in the pad bath solution. The fabric from this treatment looks Whiter in regular and ultraviolet light than fabric treated with the same pad bath solution without the copolymer.

Another variation of these approaches is possible with precured fabric. For this purpose, the precured fabric is given an afterwash in a solution containing an optical brightener. :Under these conditions, the washed fabrics treated with crosslinking agent and polyvinylpyrrolidoneacrylate copolymer or fabric treated with crosslinking formulation, optical brightener and copolymer appear whiter than the control fabrics treated with the same formulations, which did not contain any vinylpyrrolidoneacrylate copolymer.

In general, the process of this invention is the incorporation of the polyvinylpyrrolidone-acrylate copolymer in normal pad bath solutions to produce wash-wear or durable press cotton. From this point on, the fabrics are finished in a standard manner according to contemporary textile practice. This method can be used with a number of textile formulations, the only requirement being that a certain amount of water be replaced with an equivalent amount of copolymer. For precured fabrics, the modification of using an optical brightener in the afterwash or as a component in a solution in a second afterwash represents some variation from current textile practice on precured fabric.

The vinylpyrrolidone-acrylate copolymer is effective in pad bath concentrations ranging from 0.3% to The preferred range in copolymer concentration for overall performance appears to be from 2% to about 6%.

The following examples are intended to be representative of treating solutions rather than limiting. Numerous variations are possible for anyone practiced in the textile art.

4 EXAMPLE 1 A solution was prepared using 7 parts dimethylol dihydroxyethyleneurea, 0.5 part zinc nitrate hexahydrate catalyst and 0.5 part vinylpyrrolidone-acrylate copolymer and 92 parts water. The mixture was padded onto cotton fabric, dried 7 minutes at 60 C. and cured 10 minutes at 130 C. Similar solutions were prepared using the same formulation except that the amount of copolymer was 1, 2, and 4 parts and the amount of water was reduced to 91.5 parts, 90.5 parts, and 88.5 parts.

Also treated was a crosslinked control in which the padding solution was 8 parts dimethylol dihydroxyethyleneurea, 0.6 part zinc nitrate hexahydrate catalyst, and 91.4 parts water. After the fabrics were padded with these various solutions, dried and cured, they plus an untreated sample were washed in a solution containing g. of a detergent which contained an optical brightener. The fabrics which contained increasing amounts of polymer were progressively whiter relative to the crosslinked control. Similarly under UV light, the fabrics treated with copolymer were white while the crosslinked control without copolymer was gray. Finally, the fluorescence values of the various fabrics were measured. The results are reported in Table I together with appropriate wrinkle recovery angles and tearing strength values of the respective fabrics. In this table, fluorescent values are reported as a percentage of the fluorescent value of the noncrosslinked cotton control. It is apparent from the table that as progressively larger amounts of copolymer are used in the treatment higher fluorescent values were obtained on the fabric indicative of better absorption of optical brighteners. Values for wrinkle recovery and tearing strength indicate additional improvement in performance in these properties from the use of copolymer in the finish.

Parts of these fabrics were laundered 10 times. The samples treated with copolymer were similarly whiter than the controls without copolymer under both regular and UV light. The appropriate column in Table I shows the durable nature of these treatments, because all samples with copolymer had superior fluorescent values.

A solution was prepared using 7 parts dimethylol dihydroxyethyleneurea, 0.5 part zinc nitrate hexahydrate catalyst, 1 part of polypropyleneglycol (mol. wt.=340), and 1 part alkyl ethyleneoxide alcohol (C alkyl group-60% of additive mol. wt. due to ethyleneoxide polymer component), 0.5 part vinylpyrrolidone-acrylate copolymer, and 90 parts water. The mixture was padded onto cotton fabric, dried 7 minutes at 60 C. and cured 10 minutes at C. Similar solutions were prepared using the same formulation except that the amount of copolymer was 1, 2, and 4 parts and the amount of water was 89.5, 88.5, and 86.5 parts. Also treated were two controls. One control was the crosslinked control in which the padding solution was 8 parts dimethylol dihydroxyethyleneurea, 0.6 part zinc nitrate hexahydrate catalyst, and 91.4 parts water. Another control was run in which a fabric was treated with 7 parts of dimethylol dihydroxyethyleneurea 0.5 part zinc nitrate hexahydrate catalyst, 1 part of polypropyleneglycol (mol. wt. 340) and 1 part alkyl ethyleneoxide alcohol (C alkyl group-60% of additive mol. wt. due to ethyleneoxide polymer component) and 90.5 parts water. After all fabrics were dried and cured, they were laundered in the presence of a detergent containing optical brightener. The fabrics which contained increasing amounts of polymer were progressively whiter relative to the crosslinked control. Similarly, under UV light, the fabrics treated with copolymer were white while the crosslinked control without copolymer was gray. Finally, the fluorescence values of the various fabrics were measured. The results are reported in Table II together with appropriate wrinkle recovery and tearing strength values of the respective fabrics. The results in Table H demonstrate that the combination of polyether and vinylpyrrolidone-acrylate copolymer has higher fluorescent values than those obtained with either polymer alone in Table I or the polyether control in Table II.

then measured using the untreated cotton control (100%) as the standard. Under these conditions, the sample treated with crosslinking agent and zinc nitrate (conventional treatment) had 30% of the fluorescence of the untreated cotton While the sample treated with copolymer had 39% of the fluorescence of the untreated cotton. These samples indicate that the use of these treatments improves optical brightener absorption of blended fabrics. However, the amount of improvement does not seem to be as great as for all cotton fabrics with comparable treatments due to the poor absorption characteristics of the polyester fiber.

We claim:

1. A process for imparting to a cellulosic fabric dur- 1 Polyether and copolymer were those described in treating formulations in Example 2.

For example, a combination of 2% copolymer and 2% reactive ethers had 54% of the fluorescent value of the untreated cotton after the first wash and 47% after the tenth wash. By contrast, the crosslinked control had only 11% of the fluorescent value of the untreated cotton after the first wash and 12% of the value of the untreated cotton after the tenth wash. Again, these results indicate that the use of vinylpyrrolidone-acrylate copolymer represents an effective approach to improving the optical brightener absorption and hence whiteness of durable press fabrics. The cumulative elfect of the use of increasing amounts of polymer caused increasing fluorescent values of the finished fabrics. Wrinkle recovery and tearing strength were likewise improved by the use of copolymer in these finishes.

EXAMPLE 3 -A polyester-cotton fabric (50-50 blend) was used in which the polyester component had optical brightener. One sample was padded with a mixture of 7 parts of dimethylol dihydroxyethyleneurea, 0.5 part of zinc nitrate hexahydrate, parts of vinylpyrrolidone-acrylate copolymer and 87.5 parts of water. The other sample was the control (50-50 polyester-cotton), whic hwas padded with 9 parts of dimethylol dihydroxyethyleneurea, 0.5 part of zinc nitrate hexahydrate, and 90.5 parts of water. After the samples had been dried for 7 minutes at 60 C., they were cured for 10 minutes at 130 C. These samples were than washed together with an untreated cotton sample in the presence of 100 grams of a commercial detergent containing original brightener. When the fluorescence of the resulting fabrics was measured using a value of 100% for the untreated cotton, then the polyester-cotton with crosslinking agent and copolymer had a value of 44% while the polyester cotton with crosslinking agent only had a value of 38%. In another case, 50-50 polyester cotton was treated with a solution containing 7 parts dimethylol dihydroxyethyleneurea, 0.5 part zinc nitrate hexahydrate, 1 part of polypropyleneglycol (mol. wt.-=340) and 1 part of alkyl ethyleneoxide alcohol (C alkyl group- 60% of additive mol. wt. due to ethyleneoxide polymer component), 2 parts of vinylpyrrolidone-acrylate copolymer and 88.5 parts of water. The fabric was dried and cured in a similar manner as the previous samples. This fabric, the polyester-cotton crosslinked control (sample treated with dimethylol dihydroxyethyleneurea, zinc mtrate, and water) and the untreated cotton control were laundered ten times in the presence of a commercial detergent. The fluorescent values of the various fabrics were able-press properties correlated with high optical brightener absorption, comprising:

(a) impregnating a cellulosic fabric with a solution containing about from 4% to 15% of an agent for crosslinking cellulose, about from 0.1% to 3.0% of an acidic agent for catalyzing the crosslinking reaction between the cellulose of the fabric and the crosslinking agent, about from 0.3% to 15.0% of a vinylpyrrolidone-acrylate copolymer having the formula cH,--CH= R (1H2 =0 (l) wherein R' represents a hydrogen or a methyl group; R represents a carbon chain of from 4 to 18 carbons in length; and the x and y moieties of the polymer can be at ratios of about from 3:7 to 7:3, respectively, and water; and

(b) dry curing the resulting wet, impregnated fabric.

2. The product produced by the process of claim 1.

3. A process for imparting to a cellulosic fabric durable-press properties correlated with high optical brightener absorption, comprising:

(a) impregnating a cellulosic fabric with a solution containing about from 4% to 15% of dimethylol dihydroxyethyleneurea, about from 0.3% to 1.5% of zinc nitrate hexahydrate catalyst, about from 0.3% to 15.0% of a vinylpyrrolidone-acrylate coplymer having the formula wherein R represents a hydrogen or a methyl group; R represents a carbon chain of from 4 to 18 carbons in length; and the x and y moieties of the polymer can be at ratios of about from 3:7 to 7:3, respectively, and water;

(b) drying the resulting wet, impregnated fabric for about from 5 to 10 minutes of about 60 5.; and

(b) drying the resulting wet, impregnated fabric for about from 5 to 10 minutes at about 60 C.; and

(c) curing the dry, impregnated fabric for about 10 oxide alcohol wherein the alkyl group is a twelve minutes at about 130 C. carbon chain and 60% of the additive molecular 4. The product produced by the process of claim 3. weight is due to ethyleneoxide polymer component, 5. A process for imparting to a cellulosic fabric durabout from 0.1% to 1% of a polypropylene glycol able-press properties correlated with high optical bright- 5 having a molecular weight of 340, and water; ener absorption, comprising: (b) drying the resulting wet, impregnated fabric for (a) impregnating a cellulosic fabric with a solution about from 5 to 10 minutes at about 60 C.; and

containing about from 4% to 15% of dimethylol (c) curing the dry, impregnated fabric for about 10 dihydroxyethyleneurea, about from 0.3% to 1.5% of minutes at about 130 C.

zinc nitrate hexahydrate catalyst, about from 0.3% to 10 6. The product produced by the process of claim 5. 15.0% of a vinylpyrrolidone-acrylate copolymer having the formula References Cited CH:CH2 R UNITED STATES PATENTS H, =0 ('1 3,658,457 4/1972 Blanchard et a1 8116.3 5 15 3,484,838 12/1969 Press 260-895 .5 g 3,104,934 9/1963 Blumenkopt s 11s.s EH13 -q- 3,142,664 7/1964 Bauer 260--80.5 LR |y 3,232,912 2/1966 Munday et a1. 260-80 wherein R represents a hydrogen or a methyl group;

R represents a carbon chain of from 4 to 18 carbons 20 JOHN COOPER Primary Exammel' in length; and the x and y moieties of the polymer U S Cl XR can be at ratios of about from 3:7 to 7:3, respectively, about from 0.5% to 1% of an alkyl ethylene- 8115.6, 116.3, 85, 1 W, 31; 260-86.1 N; 117--33.5 T 

